The purpose of this proposal is to develop techniques for determining the nature of tinnitus experienced by animals so that the mechanisms underlying tinnitus can be studied experimentally. The type of tinnitus to be studied is the transient tinnitus caused by exposure to loud tones. The project consists of three parts. First, a two-choice procedure will be developed to determine the pitch of an animal's tinnitus. Rats will be trained to rank-order the pitch of external sounds presented to each ear separately via headphones. They will then be tested on their ability to match the pitch of tinnitus that is induced in one ear with external tones presented to the other ear. Second, the auditory brainstem response (ABR) will be calibrated for use as a rapid means of determining hearing loss caused by exposure to loud tones. We will obtain both behavioral and ABR thresholds in the same animals before and after exposure to loud tones. The results will show if the two measures give the same estimate of hearing loss and, if not, whether a correction factor can be used to determine the behavioral hearing loss from the ABR. Finally, the cochleas of the animals used in the development of these procedures will be examined to obtain exploratory information regarding the relation between tinnitus, hearing loss, and damage to the Organ of Corti. The ultimate goal of this project is to devise tools to be used to discover the cause of tinnitus and to develop effective treatments. Knowing the pitch of an animal's tinnitus is necessary to distinguish between physiological changes due to hearing loss from those due to tinnitus. [unreadable] [unreadable]